Move the Settings flow from the Chats flow up one level to the UserSession flow. (#4390)

* Add the basis for a state machine to UserSessionFlowCoordinator.

* Move the Settings flow from the Chats flow to UserSession flow.

It now works from the Spaces tab.

* Add a StateMachineFactory and use it to publish the state in the tests.

ElementX/Sources/Services/StateMachine/StateMachineFactory.swift

@@ -0,0 +1,51 @@
+//
+// Copyright 2025 New Vector Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+// Please see LICENSE files in the repository root for full details.
+//
+
+import Combine
+import Foundation
+import SwiftState
+
+protocol StateMachineFactoryProtocol {
+    func makeUserSessionFlowStateMachine(state: UserSessionFlowCoordinator.State) -> StateMachine<UserSessionFlowCoordinator.State, UserSessionFlowCoordinator.Event>
+    func makeChatsFlowStateMachine() -> ChatsFlowCoordinatorStateMachine
+}
+
+struct StateMachineFactory: StateMachineFactoryProtocol {
+    func makeUserSessionFlowStateMachine(state: UserSessionFlowCoordinator.State) -> StateMachine<UserSessionFlowCoordinator.State, UserSessionFlowCoordinator.Event> {
+        .init(state: state)
+    }
+    
+    func makeChatsFlowStateMachine() -> ChatsFlowCoordinatorStateMachine {
+        .init()
+    }
+}
+
+// MARK: For testing
+
+class PublishedStateMachineFactory: StateMachineFactoryProtocol {
+    let baseFactory = StateMachineFactory()
+    
+    // MARK: UserSessionFlowCoordinator
+    
+    let userSessionFlowStatePublisher = PassthroughSubject<UserSessionFlowCoordinator.State, Never>()
+    
+    func makeUserSessionFlowStateMachine(state: UserSessionFlowCoordinator.State) -> StateMachine<UserSessionFlowCoordinator.State, UserSessionFlowCoordinator.Event> {
+        let stateMachine = baseFactory.makeUserSessionFlowStateMachine(state: state)
+        stateMachine.addAnyHandler(.any => .any) { [weak self] in self?.userSessionFlowStatePublisher.send($0.toState) }
+        return stateMachine
+    }
+    
+    // MARK: ChatsFlowCoordinator
+    
+    let chatsFlowStatePublisher = PassthroughSubject<ChatsFlowCoordinatorStateMachine.State, Never>()
+    
+    func makeChatsFlowStateMachine() -> ChatsFlowCoordinatorStateMachine {
+        let stateMachine = baseFactory.makeChatsFlowStateMachine()
+        stateMachine.addTransitionHandler { [weak self] in self?.chatsFlowStatePublisher.send($0.toState) }
+        return stateMachine
+    }
+}